Employee Benefit Plans (Reconciliation of Assets Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 4	$ 33
Purchases	24	50
Sales	(1)	(15)
Total gains (losses) and other, net	21	(7)
Ending balance	15	4
Master Trust [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	34	37
Sales	(2)	(4)
Total gains (losses) and other, net	(1)	1
Ending balance	$ 31	$ 34